Bicycles have become a common mode of human-powered transportation. In conventional so-called upright bicycles, such as the multi-speed racing bicycles and the mountain style bicycles, the seat is positioned between and above the wheels while, the pedal assembly is positioned essentially vertically downward from the scat.
The conventional so-called upright bicycles suffer from a set of drawbacks. One of the main drawbacks associated with the so-called upright bicycles is that a relatively high proportion of the effort expanded by the rider is used to overcome wind resistance.
Another drawback of the conventional upright bicycles relates to the fact that the rider sits relatively high away from the ground and that in the event that a high degree of deceleration is achieved, the rider may be projected forwardly. Furthermore, hard braking can also lead to severe skidding of the tires.
A still further drawback of the conventional so-called upright bicycles is the general lack of ergonomic characteristics associated with the rider's position.
In order to circumvent the above mentioned disadvantages, another type of bicycle has evolved throughout the years, namely the so-called recumbent bicycle. The recumbent bicycles differ from the conventional upright bicycles in that the rider sits behind the foot pedals in a recumbent or reclining position on a seat that is usually provided with a backrest.
Unlike in an upright bicycle in which the rider's legs extend generally downwardly, in a recumbent bicycle, the rider's legs extend forwardly substantially parallel to the ground. As such, the combined frontal area of a recumbent bicycle and the rider is typically substantially less than in a conventional upright-type bicycle, thus causing less wind resistance.
Furthermore, the lower center of gravity and feet forward riding position mean that a high degree of deceleration can be achieved without the rider being projected forward. The risk of injury to the body due to contact with the handlebars, brakes and gear shift levers is reduced in the event that the rider is thrown forward. The feet being positioned in front of the rider, they are most likely to make contact in a head on collision, often bracing the rider and preventing substantial injury.
Moreover, during pedalling, the loads applied to the rider's body against the seat in reaction to the forces applied to the foot pedals by the rider's legs are transmitted to the seat through the hips and shoulders of the rider. This enables the upper torso and arms of the rider to remain relaxed while full power is being applied to the foot pedals.
Furthermore, the seat of a recumbent bicycle typically supports more of the rider's body area, including his back, so that the weight of the rider is distributed over a larger surface for greater comfort. Also, the recumbent position allows for greater thrust power since the back of the rider can be braced against the seat.
Although the recumbent bicycles generally present major advantages over the conventional upright bicycles, some of the prior art recumbent designs suffer from a set of drawbacks.
A first subset of drawbacks is related to the fact that in some of the prior art recumbent bicycles, the position of the seat is relatively fixed with respect to the position of the pedals. Consequently, various sized frames are required for different sized riders. This, of course, affects the bicycle manufacturing cost as well as the inventory requirements of both bicycles' suppliers and retailers.
In U.S. Pat. No. 4,878,684, issued Nov. 7, 1989, Eugene W. Lemle addresses the problem of using different sized frames for different sized riders by proposing a recumbent bicycle having a seat that can be quickly repositioned on the frame so as to provide for an adjustable spacing between the seat and the pedal assembly.
Although the solution thought by U.S. Pat. No. 4,878,684 solves the problem of providing various sized frames to accommodate various sized riders, it creates a set of new drawbacks. Indeed, in order to accommodate riders of all sizes, manufacturers resort to building relatively long frames so that riders having relatively long legs can be properly positioned by using the frame to its full length, while smaller sized riders are accommodated by moving the seat frontwardly on the relatively long frame towards the pedal assembly. The resulting effect is that medium sized and smaller sized riders must resort to using an oversized frame designed to accommodate larger sized riders.
The medium sized and smaller sized riders are thus forced to use an oversized frame that affects some important riding characteristics. The oversized length of the frame affects the capacity of the recumbent bicycle to corner a relatively tight curve. This can prove to be a particularly important problem in urban areas wherein relatively tight curves are quite frequent.
Another problem associated with the re-positioning of the seat on the frame relatively to the pedal assembly is that the weight distribution and the overall geometry of the bicycle are changed dramatically, thus affecting the overall stability of the recumbent bicycle.
Another disadvantage of changing the overall weight distribution and geometry of the bicycle is that the steering geometry and thus the steering "effect" of the bicycle is different than that which the rider is typically accustomed to.
Another drawback associated with the use of an oversized frame is the difficulty for smaller riders to mount unto the bicycle and to dismount from the latter.
A still further problem related to the re-positioning of the seat relatively to the pedal assembly is that the re-positioning of the seat also necessitates a re-positioning of various other components such as the handlebars, the brake levers and the gear shift levers.
A second subset of drawbacks frequently encountered with prior art recumbent bicycles, whether of the adjustable type or not, is related to the lack of ergonomic design of the seat. Since, as mentioned previously, the reaction to the thrust power on the pedals is applied against the back of the rider by the seat, the seat, if not designed properly, can lead to various injuries, especially in the lumbar region.
A third set of drawbacks associated with various prior art recumbent bicycles is that being positioned relatively close to the ground, some of their structural components are susceptible of contacting the road surface when the bicycle is sidewardly tilted during the cornering of a curve.
A fourth set of drawbacks associated with most conventional recumbent bicycles, especially bicycles wherein the seat may be re-positioned relative to the pedal assembly, is that they are mechanically complex and thus difficult to assemble and disassemble and thus are not adapted to be readily disassembled for storage and transportation.
A fifth set of drawbacks associated with most conventional recumbent bicycles is that since the gear shifting mechanism is positioned relatively close to the road surface, relatively small gear systems have been used so as to minimize the risk of the gear systems coming into contact with the ground surface when the vehicle corners a curve. Consequently, most prior art recumbent bicycles are not provided with a large gear ratio.
There is therefore a need for a recumbent-type bicycle that would be adaptable to various sized riders, while not presenting the drawbacks associated with using an oversized frame. A recumbent-type bicycle offering various ergonomic features such as an ergonomic seat and a high gear ratio is also highly desirable.